Multipack negative system



March 7, 1933.

Fronl Flm Rear film Fronl Fllm Rear filml H. W. MOYSE MULTIPACK NEGATIVE SYSTEM Filed June 2o, 1930 film Base Orlhochromallc Emulsion lDual Collold louer .lffClr Colloid Lauer Panch romalic Emulsion Film Base Fllm base /Dued Emulsion Ficll .-fcledr Colloid La er Panchromollc Emulsion F i lm Base his @Horne wlw/4% Patented Mar. 7, 1933 HOLLIS W. MOYSE, OF NEW BRUNSWICK, NEW

JERSEY, ASSIGNOR TO DU PONT IFILM MANUFACTURING CORPORATION, F WILMINGTON, DELAWARE, A CORPORATION OF DELAWARE y Application led June $20,`

ing color separation negatives for use in color photography. Many of these methods require specia cameras with ilter attachments, prisms, reflectors,etc. Perhaps the easiest method for making color separation nega- 1Q tives has been the bi-pack and tri-pack arrangements wherein two or three negatives are stacked uponeach other and loaded in the ordinary cameras. This system of color separation 1s, however, subject to certain dis -advantages one of which is the lack of sharpness of the image produced on the rear emulsion in the bi-pack negative-system and on the middle and rear emulsions in the tri-pack negative system.

. This invention duction of a multi-pack negative system having improved means associated therewith capable of minimizing-the tendency to lack of sharpness in the rear lm or lms. A further ob]ect is the production of a multi-pack negative system in which the aforesaid means is applied as a coating to the surface of a rear emulsion.

These obj ects are accomplished by the following invention in which a layer or lm of transparent colloid is positioned between the emulsion of a rear negative and the light filtering means of a front. negative, the co1- loid layer being coated on the surface of an emulsion, preferably on the surface of the rear emulslon.

In the drawing:

Fig. l is a section through one form of bipack system` illust-rating my improvement associated therewith and Fig. 2 showsmy improvement associated j with another form"y .of b1- pack. lm. A

In the form shown in Fig. 1, the front film or negative is composed of alm base 1 carrying an orthochromatic-emulsion 2 sensitive to blue and green light rays. The numeral .3 is a color screen composed of a coating Tofdyed or stained colloid. which lters out all but the red rays passing to the panchromatic Aemulsion 5 onth'e ilm base 6.' A coating 4 has as an object the pro- MULTIPACK NEGATIVE SYSTEM 1930. Serial N0. 462,471.

' of `transparent undyed colloid is applied to the surface of the rear emulsion 5.

The colloid coatings 3 and 4 may be made from solutions of colloids such as gelatin, agar, casein, etc., which are coated on the emulsion layer in a separate operation during manufacture in the same manner that ,the emulsion is coated.

The sharpness of the image on'a rear negative of multi-pack systems is largely dependent upon the degree of contact the emulsion surface of the rear film makes with the emulsion surface of the front film. A colloid layer, such as gelatin, as will be apparent, will make better contact with an emulsion surface than one emulsion will make with another. V'The light scattering effect ofy the emulsion surfaces is, however, the main reason for the lack of sharpness ofthe image on the rear film: A negative emulsion surface is granular or discontinuous and has a distinct matt appearance due to the separate particles of silver bromide crystals. The light is scattered and diffused by such a surface, the effect increasing with increasing separation of the emulsion surfaces. A colloid layer, on the other hand, has a vsmooth continuous surface permits the light rays to pass with less distortion from one emulsion to the other.

The light filtering screen consisting of av possible the formation of a still sharper image on the rear emulsion than does the dyed'col- V.loid alone. 'When a single layer of colloid is used, as in the application referred to, the

-layer can be applied as acoating to only one .emulsion and the contact of the layer with which together -with the better contact with the emulsion,

the adjacent emulsion is, of course not so intimate. In thepresent invention wherein the colloid is applied as'a coating to both `emulsions,the contact between the adjacent 'colloid surfaces is better than the contact one surface of a single coating makes with emulsion surface adJacent the one to which the coating is applied. The advantages gained from the better contact more, than oifset any tendency to get slight diffusion on the rear film due to the separation caused by the colloid layers.

In the preferred form'of the inventionl as described above, my improvement is associated with a multi-pack negative system in which a front emulsion has applied thereto a layer of dyed colloid. The present invention is, however, applicable to multi-pack negative systems in which the light ltering means is associatedwith a front emulsion 1n a man-l ner different than that previously referred to. f.

In Fig. 2 a coating of dyed or stained emulsion 2 is applied to the ilm base 1 and the coating of clear undyed colloid 4 is coated on to the surface of the rear or second emulsion 5 carried b the base 6" as in Fig. 1. As

previously note the sharpness of the image LQUOABQ thereof, except defined in the 'appended claims.

I claim: 1. .In a multi-pack negative system; a front light sensitive emulsion having coalescently coated thereon a relatively thin, transparent, water-permeable, dyed colloid, to minimize the scattering of light, and a rear emulsion having a like coating thereon thatA is undyed. e u

on the rear emulsion' is dependent upon the closeness of Contact of the emulsions, and, as will be apparent the surface of the dyed emulsion 2 will make better contact with the smooth surface of the colloid layer 4 than it would with the surface of emulsion 5'.

The term light ltering means as used herein comprises, therefore, the dye or stain in the emulsion itself as well as the layer of dyed colloid illustrated in Fig. 1.

While I have found a coating of a colloid to be the most effective as a medium for carrying out the inventionr'itwill be 'apparent that-the invention is not restricted to this class of materials but may be practiced `by using coatings of materials' having subf' stantially the same characteristics as colloid coatings. 4 When the clear colloid layer 4 or 4 is coated on the kemulsion surface, a. fusion takesj place and since there .is no diiference in the index of refraction 'between the colloid of the emulsion and the colloid of th'elayer it becomes impossible to detect any surface at the original face of the emulsion. The cleal` colloid layer 4 could if desired, be coated onto the surface ofthe dyed emulsion 2.

The fuzzy rear image resulting from the difusionlof light from the matt surfaces of the emulsion layers has been a serious defect in the known -bi-pack negative systems. These defects are practically eliminated or minimized by layers as hereinldisclosed.

nieans of the colloid layer or As many apparently widely embodiments of this invention may be'made without'depart/ing from the spirit and scope thereof, it is to'be understood that I `do not limit myself to the specific embodiments 

